[time-nuts] Lead acid battery noise levels

J. Forster jfor at quikus.com
Thu Jul 11 12:16:03 EDT 2013


It's a compromise. NiCds are quiet, but they have to be recharged and can
have high self-discharge rates and grow whiskers internally.

If I were building a one-off or a few amps, and Hg batteries were
plentiful in the stockroom, I might well use them also.

In the PAR 113 the NiCd pack has to be replaced pretty often. The unit is
either in battery charge or operate mode. They do not 'float charge'. If
you get them used, the battery was not even wirth testing. Digi-Key would
make up replacements for $100-$150, but that was a while ago.

I don't know if you can noise model a battery as an ideal voltage source
in series w/ a Thevenin Equivalent, and use the Thevenin resistance in
SQR(4KTBR), but it seems at least plausible.

This would explain why bigger batteries reported;y have lower noise, at
least in part.

-John

================




> A long time ago, when I was concerned about a phase noise issue, I found
> an
> old NBS article. It was on measuring phase noise and included a schematic
> of
> an ultra-low noise amplifier. In that amplifier they used Mercury
> batteries.
> I also glanced at the referenced article, stating NiCad is the lowest
> noise,
> and, NiCads were available for a long time, yet they used Mercury.
> Regards
> - Mike
>
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of David Kirkby
> Sent: Thursday, July 11, 2013 10:25 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Lead acid battery noise levels
>
> On 11 July 2013 05:47, Mark Spencer <mspencer12345 at yahoo.ca> wrote:
>> Eric:
>>
>>  http://tf.nist.gov/general/pdf/1133.pdf
>>
>> discusses the noise levels of various batteries.
>>
>> Regards
>> Mark S
>
>
> Sod's Law comes into play here. From a quick read of that, it seems NiCd
> are
> best, but they are being phased out. I was told they were banned in
> Europe,
> but I don't know if that is true. I'm pretty sure I've seen NiCd tools in
> the local DIY store, so I doubt it is true.
>
> Dave
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